1. Field of the Invention
This invention relates to mechanical connection systems enabling plates, notably glazing elements, to be fixed to a supporting structure. The invention is concerned more especially with the fixing of glazing elements to a supporting structure by a technique consisting of fixing said elements, not by their periphery by means of a peripheral frame, but by means of mechanical hooking points, usually situated at each of their corners.
2. Description of the Related Art
Glazing elements fixed in this manner are known as suspended external glazings or structural glazings (hereinafter referred to simply as structural glazings). This type of fixing, which is very unobtrusive, makes possible the construction of outer walls for buildings constituted entirely of glazing elements, some being transparent to fulfill the function of viewing panes, the others opaque and generally fulfilling the function of a wall. Such external walls exhibit a minimal surface discontinuity as seen from the outside.
The desire for an aesthetic appearance, however, should not be allowed to detract from the reliability of the fixing, and the design of these point connections should take into account various requirements from a mechanical aspect. Thus, these connections must guarantee a firm and effective transverse fixing between the glazing element and the carrying structure which will support the weight of the glazing element without risk of breakage. On the other hand, the glazing element, once in position, must be capable of responding without breaking to loads of various natures, and in particular to stresses which have a tendency to flex the element, such as wind induced stresses. The connection should therefore allow a flexure of a few degrees in the glazing element.
Lastly, if the glazing element should be a multiple pane of the double glazing type, where different glazing plates are assembled with a gas space between them by means of a peripheral seal, it is important not to subject said seal to excessive shear forces resulting from the transfer of the weight of the glazing plates to the plate that is effectively fixed to the structure.
Various fixings for panes of such structural glazings have already been proposed. For example, in European Patent Application EP-A-0 192 472, there are described fixings elements for a double glazing making possible, by simple screwing with a milled countersunk screw, the tightening of one or another of the panes of the double glazing against the supporting structure. There is, however, no connection between the two sheets of the double glazing which can resist the longitudinal sliding of the sheet that is not fixed by this through screw. This places a heavy load on the peripheral seal of the double glazing. Moreover, if the fixing described allows a certain flexibility of the double glazing after it has been fixed, this is due only to the presence of seals of compressible material, which allow a certain deflection of this screw relative to the orifice or orifices formed in the sheet or sheets of the double glazing. This flexibility is therefore both very small and uncontrollable.
There is also known, notably from European Patent Application EP-A-0 506 522, a system of mechanical connection which enables the positioning of the glazing element relative to the structure to be corrected or, in the case of multiple panes, all the successive orifices perforated through each of the sheets of said panes to be recentered, this being achieved by means of a system of eccentric rings placed in one of said orifices. A swivel joint system is also provided and comprises a ball member and a socket member. It permits the double glazing to tilt in a spherical movement about the center of the swivel joint, which is located in the gas cavity of the double glazing. The flexibility of the pane is thereby guaranteed but the swivel joint requires a perfect fit between the head of the ball and the hemispherical cavity in which it is to be seated in order to prevent any risk of jamming between these two components. High accuracy with regard to the dimensioning of the components is therefore necessary, which leads to fairly high manufacturing costs.